Where in the world can you find today’s oldest existing fortress? How many people does it take to build a castle? What is the heaviest-sized boulder that could be thrown by a trebuchet? Find out the answers to these questions and more in , which features photographs of fortresses from around the world, as well as maps, models, and dioramas to help young readers visualize all the exciting facts and information. From the earliest stone strongholds to the most elaborate fairy-tale fortresses in Germany, India, and Japan, kids will learn about every aspect of life in medieval society, including farming, food and feasting, entertainment, and, of course, knights! Vetted by educational consultants, the DKfindout! series drives kids ages 6–9 to become experts on more than 30 of their favorite STEM- and history-related subjects, whether Vikings, volcanoes, or robots. This series covers the subjects that kids really want to learn about—ones that have a direct impact on the world around them, like climate change, space exploration, and rapidly evolving technology—making learning fun through amazing images, stimulating quizzes, and cutting-edge information. The DKfindout! series is one that kids will want to turn to again and again.